LED lighting systems are becoming increasingly popular as the cost of LEDs drops due to manufacturing efficiencies. These LED lighting systems typically utilize a plurality of connected LEDs to produce a desirable light output intensity and brightness. In many cases, because of better power efficiency and much longer lifetime, existing lighting fixtures are being retrofitted to accommodate LEDs as replacements. By way of example, many incandescent lighting systems have been retrofitted to use LEDs.
While LEDs are being used as replacements in existing lighting systems, as in the case of incandescent lighting systems, most customers desire the same features in LED lamps that are provided in the incandescent systems. One such feature is an ability to dim the light to provide proper ambience and energy savings. LEDs, however, generally cannot be directly connected to conventional dimming circuits. For example, an LED driver directly connected to a conventional dimmer cannot easily and efficiently operate at lower dimming levels, or could be damaged by current spikes. Therefore, a number of conventional approaches have been devised to provide a dimming capability designed specifically for LED lighting systems.
Many of the conventional dimming systems and techniques include the use of an integrated circuit (IC) to provide a control signal for power switching and current regulation. These control ICs, however, can be expensive and can require complex control strategies. Also, most dimming control ICs require additional power switches to provide adequate bleeding and/or damping. ICs can therefore be problematic.